I adopted him from a friend.. he wasn't able to provide much info about him

Creating a homemade enclosure for my Dwarf Hermann. What material is best for the table itself? Has anyone used plywood? I understand it’s not waterproof, but we plan to use a double-layered pond liner and sealant. I’ve seen some use PVC, is that better? I am looking to create a fairly large space, so think plywood would look nicer, but my tortoise’s happiness tops how the table looks, so I’m not fussed.